1. Field of the Invention
The present invention relates to an electronic compass which comprises a magnetic sensor for detecting a geomagnetism to obtain azimuth data, and has a function of optically indicating a plurality of arbitrarily set azimuths on the basis of the azimuth data obtained by the magnetic sensor.
2. Description of the Related Art
In order to know a direction to move from a predetermined point to the next given point in a state wherein there is no index for discriminating an azimuth, a magnetic compass on which a magnetic needle is rotatably mounted to always direct "north" by a geomagnetism is used. An electronic compass is also known. In this compass, two magnetic sensors such as magnetoresistive elements, Hall elements, or the like are arranged to be perpendicular to each other, and "north" direction data is obtained on the basis of voltages generated by the magnetic sensors, and the "north" direction is indicated by an indication device.
When a person wants to sequentially pass a plurality of points in different directions using a compass of this type, e.g., from a point A to a point B, from the point B to a point C, from the point C to a point D,..., he first grasps a direction of the point B when viewed from the point A, e.g., data indicating an angle of direction offset from the "north" direction using, e.g., a map, and then detects an actual "north" direction at the point A using a compass. The person then detects an actual direction of the point B at the point A on the basis of the detected "north" direction, and data indicating an angle of direction of the point B offset from the "north" direction obtained using, e.g., the map, and moves in the detected direction.
When the person reaches the point B in this manner, he checks the map to know a direction of the point C when viewed from the point B, detects the actual "north" direction using the compass, then detects an actual direction of the point C, and moves in the direction.
In this manner, the person can sequentially pass a plurality of points in different directions, e.g., from the point A to the point B, from the point B to the point C, from the point C to the point D,..., using the map and the compass. In this method, however, the person must check a direction of the next target point using the map, and detect an azimuth using the compass, resulting in very cumbersome operations. These operations take much time, and if the person reaches a predetermined point, he cannot immediately move in the next direction. In particular, when so-called underwater navigation to move to some predetermined underwater points using, e.g., an aqualung is conducted, it is very cumbersome to check a map at the respective points.